The invention relates to a cylinder-piston unit of a needle-free injector, with at least one cylinder accommodating an injection solution and having an outlet opening, and with at least one piston.
From an essay which appeared in the “Journal of Investigative Dermatology” (2006), volume 126 under the title “Precise Microinjection into Skin Using Hollow Microneedles” by Ping M. Wang et al., it is known to place a group of several very small hollow glass needles onto the skin of a patient who is to be inoculated, and to press them against the skin such that the glass needles, upon dispensing a liquid active substance, introduce the latter into the upper layers of skin. Since the short glass needles only have extremely thin channels, only a small amount of active substance can be dispensed, and the latter also has to have an extraordinarily low viscosity.
The object of the present invention is therefore to develop a cylinder-piston unit which is intended for a disposable injector and which is suitable for virtually painless penetration of the human skin, among other reasons for the administration of highly viscous injection solutions.